submersion

Submersion is the condition of being covered or immersed in a liquid, most often water. It can be partial, when only part of an object or body is beneath the surface, or complete, when the entire object is submerged. Submersion occurs when the surrounding fluid exerts sufficient hydrostatic pressure to interact with the object, and its duration depends on factors such as density, buoyancy, and external forces.

In physics, submersion relates closely to buoyancy. Archimedes’ principle states that a submerged body experiences an upward force equal to the weight of the displaced fluid. If the object's density is less than that of the fluid, it tends to float; if greater, it sinks. At a given depth, hydrostatic pressure increases with depth, affecting the forces on the object and any contained gases.

In practical terms, submersion is relevant to diving, marine engineering, and construction, where waterproofing, buoyancy, and depth control are designed around expected submersion conditions. In health contexts, submersion injuries describe respiratory and circulatory harm resulting from drowning or near-drowning events, with prolonged submersion leading to hypoxia, aspiration, and secondary complications.

Submersion can also describe environmental events in which land or infrastructure becomes covered by water, such as floods, tides, or coastal inundation. The concept is related to immersion, but some fields distinguish the act of submerging from the state of being submerged.